The regular expression compiler produces polymorphic opcodes. That is, the pattern adapts to the data and automatically switches to the Unicode character scheme when presented with data that is internally encoded in UTF-8 -- or instead uses a traditional byte scheme when presented with byte data.

Similarly use re 'Debug' produces debugging output, the difference being that it allows the fine tuning of what debugging output will be emitted. Options are divided into three groups, those related to compilation, those related to execution and those related to special purposes. The options are as follows:

Dump offset information. This can be used to see how regops correlate to the pattern. Output format is

NODENUM:POSITION[LENGTH]

Where 1 is the position of the first char in the string. Note that position can be 0, or larger than the actual length of the pattern, likewise length can be zero.

OFFSETSDBG

Enable debugging of offsets information. This emits copious amounts of trace information and doesn't mesh well with other debug options. Almost definitely only useful to people hacking on the offsets part of the debug engine.

Other useful flags. These are useful shortcuts to save on the typing.

ALL

Enable all options at once except OFFSETS, OFFSETSDBG and BUFFERS

All

Enable DUMP and all execute options. Equivalent to:

use re 'debug';

MORE / More

Enable TRIEM and all execute compile and execute options.

As of 5.9.5 the directive use re 'debug' and its equivalents are lexically scoped, as the other directives are. However they have both compile-time and run-time effects.
re - perldoc

# !!!!!!! DO NOT EDIT THIS FILE !!!!!!! # This file is built by mktables from e.g. UnicodeData.txt.# Any changes made here will be lost!## This file supports:# \p{Print}# # Meaning: [[:Print:]]#return<<'END';0009 000D 0020 007E ... (略) ...

Bytes in the source text that have their high-bit set will be
treated as being part of a literal UTF-X sequence. This includes
most literals such as identifier names, string constants, and
constant regular expression patterns.

On EBCDIC platforms characters in the Latin 1 character set are
treated as being part of a literal UTF-EBCDIC character.